Round trip is American English and return ticket is more British

I'm American and I say round trip. But I also know what return ticket means. Return ticket does not sound natural to me.

technically in Am English a round trip ticket contains both going and returning on the same ticket. From point A to B on one ticket is a one way ticket. Most people would just say I'm going round trip to give the understanding of going and returning with out getting into the details of "I bought two one way tickets there and back again.

In British English it's more usual to say you bought a return ticket, American English uses round trip

You can say you booked a round trip! Return is just B to A